Tripping apparatuses with force amplification are used for actuating circuit breakers. Circuit breakers designed for large currents can switch not only load currents and slight overload currents, but can also switch on high overload currents and short-circuit currents in the event of faults, and hold these fault currents for a predetermined time and switch them off again. The overload current relates to the weakest member of the equipment downstream of the circuit breaker, seen in the energy flow direction. In order to protect such downstream equipment against damage from overload or short-circuit, the circuit breaker should switch these currents, in conjunction with the power system protection equipment, within a defined time.
When the circuit breaker is switched on, energy is stored in a store, for example, a spring. In order to release this energy rapidly in the event of a fault and thus to be able to open the contacts of the switch, a very fast-acting tripping apparatus is needed.
From the prior art, a magnetic trip with force amplification is known which is used in the SUSOL 250A circuit breaker (from LS Industrial Systems). The basic principle of a magnetic catch tripping shaft with magnetic reset is used in that case. On tripping, the tripping'magnet moves a tripping catch with little force. Said catch releases a lever or shaft which is preloaded with a spring serving as a force amplifier. The shaft begins to rotate and simultaneously trips all the actuating processes that are to be realized, specifically tripping the breaker mechanism, pressing the auxiliary switch and resetting the tripping magnet. Since these actuating processes take place simultaneously, the energy of the spring is distributed among all the intended functions. For each individual actuating process, masses are accelerated and frictional and resistive forces are overcome. For each actuating process, therefore, only part of the currently effective spring force is available. The actuating processes therefore take place relatively slowly. However, a short tripping time is indispensible for rapid switching and for protecting the system against excessively large currents.
In order to achieve a short tripping time, the spring forces or those of the amplifying spring and the magnetic spring must be significantly increased. However, this entails having a magnet with a high power requirement, which significantly increases the production costs. These measures also require greater space, which is usually not available.
The switching times that are required from modern circuit breakers are, in part, no longer obtainable with the solutions that are known from the prior art. At the same time, low-energy actuators are needed for actuating the tripping catch, and this also limits the spring forces.